RESUMEN
In the last few years, the ubiquitin(Ub)/proteasome system has become increasingly recognized as a controller of numerous physiological processes, including signal transduction, DNA repair, chromosome maintenance, transcriptional activation, cell cycle progression, cell survival, and certain immune cell functions. This is in addition to its more established roles in the removal of misfolded, damaged, and effete proteins. This review examines the role of the Ub/proteasome system in processes underlying the classical effects of irradiation on cells, such as radiation-induced gene expression, DNA repair and chromosome instability, oxidative damage, cell cycle arrest, and cell death. Furthermore, recent evidence suggests that the proteasome is a redox-sensitive target for ionizing radiation and other oxidative stress signals. In other words, the Ub/proteasome system may not simply be a passive player in radiation-induced responses, but may modulate them. The extent of the modulation will be influenced by the functional and structural diversity that is expressed by the system. Cell types vary in the Ub/proteasome structures they possess and the level at which they function, and this changes as they go from the normal to the cancerous condition. Cancer-related functional changes within the Ub/proteasome system may therefore present unique targets for cancer therapy, especially when targeting agents are used in combination with radio- or chemotherapy. The peptide boronic acid compound PS-341, which was designed to inhibit proteasome chymotryptic activity, is in clinical trials for the treatment of solid and hematogenous tumors. It has shown some efficacy on its own and in combination with chemotherapy. Preclinical studies have shown that PS-341 will also potentiate the cytotoxic effects of radiation therapy. In addition, other drugs in common clinical use have been shown to affect proteasome function, and their activities may be valuably reconsidered from this perspective.
Asunto(s)
Cisteína Endopeptidasas/metabolismo , Complejos Multienzimáticos/metabolismo , Ubiquitina/metabolismo , Adyuvantes Inmunológicos/efectos de la radiación , Animales , Apoptosis/efectos de la radiación , Ciclo Celular/efectos de la radiación , Cisteína Endopeptidasas/efectos de la radiación , Humanos , Complejos Multienzimáticos/efectos de la radiación , Estrés Oxidativo/efectos de la radiación , Complejo de la Endopetidasa Proteasomal , Ubiquitina/efectos de la radiaciónRESUMEN
Several investigations have shown that illumination at night reduces melatonin level in the mammalian pineal, but the effect of night illumination on the retina is not known. In this study retinas were cultured in a flow-through apparatus and then were exposed to light at ZT 18. Light exposure reduced melatonin levels to the daytime level within 30 min. The reduction of melatonin levels was due to a rapid decrease in the activity of the enzyme AA-NAT; AA-NAT mRNA levels were not affected by illumination. Pre-incubation with lactacystin (25 microM) prevented light-induced reduction of AA-NAT activity and melatonin levels. These results demonstrate that melatonin levels in the mammalian retina are affected by light exposure at night, via proteosomal proteolysis of AA-NAT.
Asunto(s)
Acetilcisteína/análogos & derivados , Arilamina N-Acetiltransferasa/efectos de la radiación , Cisteína Endopeptidasas/efectos de la radiación , Melatonina/efectos de la radiación , Complejos Multienzimáticos/efectos de la radiación , Péptido Hidrolasas/efectos de la radiación , Estimulación Luminosa , Retina/efectos de la radiación , Acetilcisteína/farmacología , Animales , Arilamina N-Acetiltransferasa/genética , Arilamina N-Acetiltransferasa/metabolismo , Ritmo Circadiano/efectos de los fármacos , Ritmo Circadiano/fisiología , Cisteína Endopeptidasas/metabolismo , Inhibidores de Cisteína Proteinasa/farmacología , Regulación hacia Abajo/efectos de los fármacos , Regulación hacia Abajo/fisiología , Masculino , Melatonina/biosíntesis , Complejos Multienzimáticos/metabolismo , Péptido Hidrolasas/metabolismo , Complejo de la Endopetidasa Proteasomal , ARN Mensajero/metabolismo , ARN Mensajero/efectos de la radiación , Ratas , Ratas Sprague-Dawley , Retina/efectos de los fármacos , Retina/enzimologíaAsunto(s)
Cisteína Endopeptidasas/metabolismo , Cisteína Endopeptidasas/efectos de la radiación , Complejos Multienzimáticos/metabolismo , Complejos Multienzimáticos/efectos de la radiación , Piel/enzimología , Piel/efectos de la radiación , Rayos Ultravioleta/efectos adversos , Epidermis/enzimología , Epidermis/efectos de la radiación , Humanos , Peroxidación de Lípido , Estrés Oxidativo , Pronóstico , Complejo de la Endopetidasa Proteasomal , Factores de RiesgoAsunto(s)
Cisteína Endopeptidasas/metabolismo , Cisteína Endopeptidasas/efectos de la radiación , Complejos Multienzimáticos/metabolismo , Complejos Multienzimáticos/efectos de la radiación , Estrés Oxidativo , Piel/enzimología , Piel/efectos de la radiación , Rayos Ultravioleta/efectos adversos , Epidermis/enzimología , Epidermis/efectos de la radiación , Humanos , Prevención Primaria/métodos , Complejo de la Endopetidasa Proteasomal , Factores de Riesgo , Sensibilidad y Especificidad , Envejecimiento de la Piel/efectos de la radiaciónRESUMEN
Programmed cell death (PCD) is a genetically controlled cell death that is regulated during development and activated in response to environmental stresses or pathogen infection. The degree of conservation of PCD across kingdoms and phylum is not yet clear; however, whereas caspases are proteases that act as key components of animal apoptosis, plants have no orthologous caspase sequences in their genomes. The discovery of plant and fungi metacaspases as proteases most closely related to animal caspases led to the hypothesis that metacaspases are the functional homologues of animal caspases in these organisms. Arabidopsis thaliana has nine metacaspase genes, and so far it is unknown which members of the family if any are involved in the regulation of PCD. We show here that metacaspase-8 (AtMC8) is a member of the gene family strongly up-regulated by oxidative stresses caused by UVC, H(2)O(2), or methyl viologen. This up-regulation was dependent of RCD1, a mediator of the oxidative stress response. Recombinant metacaspase-8 cleaved after arginine, had a pH optimum of 8, and complemented the H(2)O(2) no-death phenotype of a yeast metacaspase knock-out. Overexpressing AtMC8 up-regulated PCD induced by UVC or H(2)O(2), and knocking out AtMC8 reduced cell death triggered by UVC and H(2)O(2) in protoplasts. Knock-out seeds and seedlings had an increased tolerance to the herbicide methyl viologen. We suggest that metacaspase-8 is part of an evolutionary conserved PCD pathway activated by oxidative stress.
Asunto(s)
Apoptosis/fisiología , Proteínas de Arabidopsis/genética , Caspasa 8/genética , Cisteína Endopeptidasas/genética , Peróxido de Hidrógeno/farmacología , Rayos Ultravioleta , Apoptosis/efectos de los fármacos , Apoptosis/efectos de la radiación , Arabidopsis , Proteínas de Arabidopsis/efectos de los fármacos , Proteínas de Arabidopsis/efectos de la radiación , Caspasa 8/efectos de los fármacos , Caspasa 8/efectos de la radiación , Muerte Celular , Cisteína Endopeptidasas/deficiencia , Cisteína Endopeptidasas/efectos de los fármacos , Cisteína Endopeptidasas/efectos de la radiación , Cartilla de ADN , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Regulación Enzimológica de la Expresión Génica/efectos de la radiación , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Estrés Oxidativo , Plantas Modificadas Genéticamente/metabolismo , Protoplastos/efectos de los fármacos , Protoplastos/fisiología , Protoplastos/efectos de la radiación , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Dynamics of postirradiation intracellular cysteine and aspartic proteinases profiles were examined in proliferating and nonproliferating Chinese hamster fibroblasts (V79). The results show that there are significant alterations in cysteine and aspartic intracellular proteinases activity already in the early postirradiation period, which are different in proliferating and nonproliferating cells. Irradiation of the cells examined to low doses and up to 15 Gy induced an increase in cysteine proteinases activity in the early postexposure period, while at higher irradiation doses applied, the activity of these proteinases was decreased. These observations suggest that intracellular proteinases are actively participating in process involving recovery from radiation injury or cell killing.
Asunto(s)
Cisteína Endopeptidasas/efectos de la radiación , Endopeptidasas/efectos de la radiación , Pulmón/efectos de la radiación , Animales , Ácido Aspártico Endopeptidasas , División Celular/fisiología , División Celular/efectos de la radiación , Células Cultivadas/enzimología , Células Cultivadas/efectos de la radiación , Cricetinae , Cricetulus , Cisteína Endopeptidasas/metabolismo , Endopeptidasas/metabolismo , Fibroblastos/enzimología , Fibroblastos/efectos de la radiación , Pulmón/enzimología , Tolerancia a Radiación , Factores de TiempoRESUMEN
UV radiation is the most important environmental skin aggressor, causing cancer and other problems. This paper reports the use of oligonucleotide microarray technology to determine changes in gene expression in human keratinocytes after UVB treatment. Examination of the effects of different doses at different times after irradiation gave a global picture of the keratinocyte response to this type of insult. Five hundred thirty-nine regulated transcripts were found and organized into nine different clusters depending on behavior patterns. Classification of these genes into 23 functional categories revealed that several biological processes are globally affected by UVB. In addition to confirming a majority up-regulation of the transcripts related to the UV-specific inflammatory and stress responses, significant increases were seen in the expression of genes involved in basal transcription, splicing, and translation as well as in the proteasome-mediated degradation category. On the other hand, those transcripts belonging to the metabolism and adhesion categories were strongly downregulated. These results demonstrate the complexity of the transcriptional profile of the UVB response, describe several cellular processes previously not known to be affected by UV irradiation, and serve as a basis for the global characterization of UV-regulated genes and pathways.
Asunto(s)
Expresión Génica/efectos de la radiación , Queratinocitos , Células 3T3 , Animales , Células Cultivadas , Cisteína Endopeptidasas/efectos de la radiación , Perfilación de la Expresión Génica , Regulación de la Expresión Génica/efectos de la radiación , Humanos , Queratinocitos/citología , Queratinocitos/efectos de la radiación , Ratones , Complejos Multienzimáticos/efectos de la radiación , Análisis de Secuencia por Matrices de Oligonucleótidos , Oligonucleótidos , Complejo de la Endopetidasa Proteasomal , Biosíntesis de Proteínas/efectos de la radiación , Proteínas/genética , Empalme del ARN/efectos de la radiación , ARN Mensajero , Transcripción Genética , Rayos UltravioletaRESUMEN
It is an intriguing question whether gravity-changing stress modulates human cell mutability. To resolve this problem, it is necessary to determine the cellular events leading to modulation. We previously detected protease activation just after UV (UVC, principally 254 nm wavelength) irradiation followed by hypomutability in cultured human cells. We here investigated whether UV-activated protease activity is affected in human UVAP-1 cells exposed to gravity-changing stress prior to UV irradiation.
Asunto(s)
Endopeptidasas/metabolismo , Endopeptidasas/efectos de la radiación , Hipergravedad , Leucina/análogos & derivados , Mutagénesis/fisiología , Rayos Ultravioleta , Ingravidez , Línea Celular , Centrifugación , Cisteína Endopeptidasas/efectos de los fármacos , Cisteína Endopeptidasas/metabolismo , Cisteína Endopeptidasas/efectos de la radiación , Inhibidores de Cisteína Proteinasa/farmacología , Humanos , Leucina/farmacología , Mutagénesis/efectos de los fármacos , Mutagénesis/efectos de la radiaciónRESUMEN
Six hours after ultraviolet B (UVB) irradiation (11.6 mJ/cm2), the viability of A431 cells decreased, and, at the same time, fragmentation of genomic DNA into nucleosomal units was observed. Z-Asp-CH2-DCB (100 microM), an inhibitor of interleukin-1 beta-converting enzyme (caspase-1) and caspase-1-like proteases, markedly inhibited UVB-induced cell death and DNA fragmentation. Both YVAD-CMK, an inhibitor of caspase-1, and DEVD-CHO, an inhibitor of caspase-3, moderately inhibited the UVB-induced cell death. A combination of YVAD-CMK and DEVD-CHO acted additionally in inhibiting cell death. These observations suggest strongly the cooperative involvement of caspases in the apoptosis induced in A431 cells by UVB.